feat(ui): dirty Ziel-Verzeichnis beim Oeffnen des Merge-Dialogs melden statt nach dem Fehlschlag

MergeTargetsDto/MergeTargets bekommen TargetDirty (via HasChangesAsync,
includeUntracked: false). Das Merge-Modal zeigt Warnung + Stash-Retry
sofort in InitializeAsync statt erst nach dem dirty_target-Fehlschlag;
der REVIEW-Block in der Detail-Pane zeigt denselben Hinweis neben
Approve. Der dirty_target-Rueckgabepfad bleibt als Absicherung bestehen.

Behebt Befund F6 aus docs/test-session-2026-09-16.md.

src/ClaudeDo.Localization/locales/en.json

@@ -328,6 +328,7 @@
       "worktree": "Worktree",
       "reviewCombinedDiff": "Review Combined Diff",
       "openDiffHint": "Open the diff to enable merge",
+      "targetDirty": "Target working directory has uncommitted changes — merging will stash and restore them.",
       "approveMerge": "Approve & Merge",
       "park": "Park",
       "parkTip": "Set aside — back to Idle, keeps the worktree",
@@ -859,7 +860,7 @@
     "tasksIsland": { "completedHeader": "COMPLETED", "completedHeaderCount": "COMPLETED · {0}", "statusPill": "{0} running · {1} review", "openTaskOne": "1 open task", "openTasks": "{0} open tasks", "planningResumeFailed": "Couldn't resume planning session: {0}", "approveFailed": "Approve & merge failed: {0}", "cancelReviewFailed": "Cancel review failed: {0}", "sendToQueueFailed": "Send to queue failed: {0}", "queuePlanBlockedInteractive": "Can't queue the plan — {0} has an open interactive session and must be closed first.", "moveRunningRejected": "Can't move a running task to another list.", "moveWorktreeRejected": "Can't move — this task has an active worktree pointing at its current repo.", "moveRepoConfirm": "Different repos — {0} → {1}. Move the task anyway?", "moveConfirmUnavailable": "Can't move — the confirmation dialog isn't available.", "quickClaudeNoWorkingDir": "This list has no working directory configured.", "quickClaudeDirMissing": "Working directory no longer exists: {0}", "setStatusFailed": "Failed to update status: {0}", "cancelFailed": "Cancel failed: {0}", "rejectToQueueFailed": "Reject to queue failed: {0}", "rejectToIdleFailed": "Reject failed: {0}", "deleteTaskConfirm": "Delete \"{0}\"? This cannot be undone.", "deleteTaskFailed": "Delete failed: {0}", "toggleDoneFailed": "Couldn't update done state: {0}", "removeFromQueueFailed": "Remove from queue failed: {0}", "openWorktreeFailed": "Couldn't open worktree: {0}" },
     "diff": { "loadFailed": "Failed to load diff: {0}", "noChanges": "No changes to show.", "unavailable": "Diff no longer available — commit range incomplete." },
     "planningDiff": { "hubError": "Could not build combined preview (hub error).", "conflict": "Cannot build combined preview: subtask {0} conflicts with an earlier subtask ({1} files).", "buildFailed": "Could not build combined preview: {0}" },
-    "merge": { "commitMessage": "chore: merge {0}", "progressMerging": "Merging…", "progressVerifying": "Running the list's verify command… ({0})", "workerOfflineBranches": "Worker offline — cannot list branches.", "loadBranchesFailed": "Failed to load branches: {0}", "merged": "Merged.", "blocked": "Blocked: {0}", "verifyFailed": "Merge landed, but the list's verify command failed — the task was kept out of Done.", "untrackedCollision": "Merge refused — it would overwrite an untracked file in the target working directory.", "dirtyTarget": "Merge refused — the target working directory has uncommitted changes.", "unknownStatus": "Unknown status: {0}", "mergeFailed": "Merge failed: {0}" },
+    "merge": { "commitMessage": "chore: merge {0}", "progressMerging": "Merging…", "progressVerifying": "Running the list's verify command… ({0})", "workerOfflineBranches": "Worker offline — cannot list branches.", "loadBranchesFailed": "Failed to load branches: {0}", "merged": "Merged.", "blocked": "Blocked: {0}", "verifyFailed": "Merge landed, but the list's verify command failed — the task was kept out of Done.", "untrackedCollision": "Merge refused — it would overwrite an untracked file in the target working directory.", "dirtyTarget": "Merge refused — the target working directory has uncommitted changes.", "targetDirty": "The target working directory already has uncommitted changes — stash them and merge?", "unknownStatus": "Unknown status: {0}", "mergeFailed": "Merge failed: {0}" },
     "settingsModal": { "workerOffline": "Worker offline — settings read-only.", "saveFailed": "Save failed: {0}" },
     "onlineInbox": { "workerOffline": "Worker offline — cannot load config.", "saved": "Config saved.", "saveFailed": "Save failed: {0}", "signedIn": "Signed in successfully.", "signedInNoRole": "Signed in, but this account is missing the 'user' role in Zitadel — online sync will be rejected until the role is granted in the ClaudeDo project.", "signInFailed": "Sign-in failed: {0}", "signedOut": "Signed out.", "signOutFailed": "Sign-out failed: {0}" },
     "tickets": { "connectionOk": "Connected as {0}.", "connectionMissingScopes": "Connected as {0}, but missing scopes: {1}", "tokenCleared": "Token removed.", "workerOffline": "Worker not reachable." },